TNF and neoplasm: Metabolites of gut microbiota (e.g., butyric acid, pentanoate, and butyrate) also induced Treg cell differentiation [158], increased the secretion of anti-tumor cytokines (e.g., IFN-γ and TNF-α) by CD8+ T cells, and enhanced the anti-tumor responses of antigen-specific CTLs and CAR-T cells [159].